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    SubjectRe: booting RAID partitions
    You wrote:
    > On 26 Aug 1998 17:43:19 -0700, MOLNAR Ingo <>
    > wrote:
    > >there is a trick though: to allocate a large enough file and determine
    > >where the contents map to, and pick out the blocks belonging to the target
    > >disk(s). Then the image can be scattered across those blocks and fed to
    > >lilo's chainloader. The image will only be on that disk. (the real image
    > >file will be a big file, sparsely containing the real image)

    [fmt'd accidentally]
    > Actually, I'd suggest something slightly better: Instead of writing
    > kernel chunks only on the first disk, those chunks may as well be
    > written on each disk, and you'd end up with a complete bootable
    > kernel on each disk. The advantage is that if you loose a disk in
    > a Raid 4/5 configuration, you still have a working kernel on each
    > of the other disks, and you can still boot in degraded mode.

    This solution seems the best of all that I've heard so far. Reserve a
    certain amount of space at the beginning of every partition included in a
    metadisk; 2 MB? A kernel and initrd image (if any) are copied into each
    component partition, in that first 1-2MB reserved space.

    Then booting off a metadisk is simple. Just list the component partitions
    on the kernel command line, line

    append = "md-root=linear,/dev/sda1,/dev/sdb1,/dev/sdc1"
    append = "md-root=raid1+0,/dev/sda1,/dev/sdb1,/dev/sdc1,/dev/sdd1"
    append = "md-root=raid5,/dev/sda1,/dev/sdb1,/dev/sdc1"
    append = "md-root=raid1,/dev/sda1,/dev/sdb1"

    md yanks the kernel and initrd off the first partition it finds.

    Installation is even easy... :)

    cat vmlinux.gz initrd.img.gz > mdimage
    dd if=mdimage of=/dev/sda1 bs=1024k # md part 1/3
    dd if=mdimage of=/dev/sdb1 bs=1024k # md part 2/3
    dd if=mdimage of=/dev/sdc1 bs=1024k # md part 3/3

    You probably want to MD5-sum the 2MB kernel/initrd space and write disk
    offsets, so the above example is a simplification.

    How does that sound?


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